The Outburst of the Very Fast Nova Aql 2009 (V1722 Aql)

Absolute spectrophotometry, high-resolution echelle spectroscopy, and BV RCIC photometry were obtained to monitor and study the outburst evolution of Nova Aql 2009. When discovered, it was setting near evening twilight, and this prevented the observations from extending past the optically thick phase. The evolution has been particularly smooth, with the V-band maximum being reached on 2009 December 17.2 at 9.90 mag. The B-band maximum preceded the IC-band maximum by 1 day, consistent with an initial fireball expansion. The reddening is high, EBV ¼ 1:35, and the distance is d ¼ 5:0 kpc, for a height above the Galactic plane of z ¼ 180 pc. The decline times of t V ¼ 7:0 and t V ¼ 16:0 days qualify Nova Aql 2009 as a very fast nova. The minimum outburst amplitude (set by the magnitude limit of preoutburst SDSS-II survey images) has been ΔRC ≥ 12:5 mag. The spectral evolution has been typical of a Fe II-type nova, with an ejecta expansion velocity of ∼915 km s 1 . The combination of a very fast decline with a slow ejectionvelocity sets Nova Aql 2009 apart from the bulk of other novae. The evolution in absolute intensity of thevarious emission lines was derived, and the time of their maximum flux determined. The Fe II emission reached its maximum value before t V ,H α around t V , and O I 8446 (excited by Bowen fluorescence from Lyβ) halfway between t V and t V. The oxygen mass in the ejecta is calculated to be 2 × 10 5 M⊙ from analysis of (O I) lines.